Arctic Tundra in a Changing Climate

The Terrestrial Research GroupLaura Gough, Coordinator

University of Texas Arlington

Arc

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Arctic LTER Mid‐Term Review18 June 2013

Arctic LTER Terrestrial PIs

• Natalie Boelman, Columbia• Donie Bret‐Harte, UAF• Eugenie Euskirchen, UAF• Ned Fetcher, Wilkes• Kevin Griffin, Columbia• Erik Hobbie, New Hampshire• Feng Sheng Hu, Illinois 

Urbana‐Champaign• Michelle Mack, Florida• Jim McGraw, West Virginia

• John Moore, Colorado State• Ed Rastetter, MBL• Adrian Rocha, Notre Dame• Josh Schimel, UCSB• Gus Shaver, MBL• Heidi Steltzer, Ft. Lewis College• Paddy Sullivan, Alaska 

Anchorage• Matt Wallenstein, Colorado 

State• Mike Weintraub, Toledo• John Wingfield, UC Davis

Senior RA: Jim Laundre, MBL

Mapping ArcLTER Objectives to Terrestrial Research

Terrestrial Research (This talk)

• “Shrubbification”– Landscape‐level response to warming– Long‐term fertilization experiments– Long‐term warming experiments– Identifying the pathways of change

• Disturbance– Vegetation resilience to fire– Successional response to thermal erosion

• Consumers– Mammalian herbivores alter response to increased nutrients

– Arthropod  consumers in shrub and open tundra

ArcLTER Shared Objectives

1. How does climate control ecosystem states, processes, and linkages?

2. How do disturbances change ecosystem states, processes, and linkages?

3. How do climate and disturbance interact to control biogeochemical cycles and biodiversity at catchment and landscape scales?

Characteristics of Arctic Tundra• soils frozen, snow‐covered most of the year

• clonal, long‐lived perennial plants dominate

• species diversity, NPP low

Giblin et al. 1991

ARC LTER Themes

• How does climate control ecosystem states, processes, and linkages? 

• How do disturbances change ecosystem states, processes, and linkages?

• How do climate and disturbance interact to control biogeochemical cycles and biodiversity at catchment and landscape scales?

“Shrubbification”

Graminoid dominated Deciduous shrub dominated

1. repeat aerial photos2. satellite imagery3. plot‐based measurements

Long‐term Nutrient AdditionMoist Acidic Tussock Tundra (MAT)

Control Annual N and P addition

Why does Betula nana (dwarf birch) respond positively to added nutrients?

• developmental plasticity – Bret‐Harte et al. 2001 Ecology

• mycorrhizae– Deslippe et al. 2011 Global Change Biology

• leaf‐level physiology– Kornfeld et al. 2012 New Phytologist– Heskel et al. 2013 Ecology and Evolution

Long‐Term Nutrient Addition

Net ecosystem loss of ~ 2,000 g C m‐2 over 20 years

Mack et al. 2004 Nature

Long‐Term Nutrient Addition

Control Fertilized

Organic

Mineral

Koyama and Wallenstein

MineralOrganicPhylum

Increased 

No change 

Decreased

Acidobacteria

Actinobacteria

Proteobacteria

Gemmatimonadetes

AD3 Chloroflexi

Verrucomicrobia

Planctomycetes

Bacteroidetes

WPS‐2

OrganicMineral

Koyama and Wallenstein

Long‐Term Greenhouse Warming

Long‐Term Greenhouse Warming

Sistla et al. 2013 Nature

Long‐Term Greenhouse Warming

Sistla et al. 2013 Nature

Long‐Term Greenhouse Warming

Sistla et al. 2013 Nature

Sistla et al. 2013 Nature

Long‐Term Greenhouse Warming

Long‐Term Greenhouse Warming

• no difference in soil C or N stocks despite differences in temperatures, thaw depth, soil communities, and plant community

• greatest biogeochemical differences at depth

• over two decades, MAT soil C and N resistant to warming

Myers‐Smith et al. 2011

ARC LTER Themes

• How does climate control ecosystem states, processes, and linkages? 

• How do disturbances change ecosystem states, processes, and linkages?

• How do climate and disturbance interact to control biogeochemical cycles and biodiversity at catchment and landscape scales?

1,000 km2 burned

Anaktuvuk River Fire 2007

Fire

Rocha et al. 2012 Environmental Research Letters

Bret‐Harte et al. in press Proc. Royal Academy London B

Hypothesis: increasing rates of thermo‐erosionaldisturbance will accelerate rates of vegetation change

Response of plant functional group abundance to thermokarst disturbance

D. dec. shrubs T. dec. shrubs

Plant functional type

Michelle Mack, unpublished

Disturbance

• tracking soil and vegetation change following pulse disturbances

• tundra may be resilient, but may also undergo several alternate successional pathways– implications for ecosystem function

ARC LTER Themes

• How does climate control ecosystem states, processes, and linkages? 

• How do disturbances change ecosystem states, processes, and linkages?

• How do climate and disturbance interact to control biogeochemical cycles and biodiversity at catchment and landscape scales?

Incorporating Trophic Interactions

Leaves and Stems

Roots andRhizomes

Live Vegetation

Leaves and Stems

Roots andRhizomes

Litter

InvertebrateHerbivores

BacteriaFungi

Soil Invertebrates

VertebrateHerbivores

Predators

Soil Nutrients

Root Exudates

Changing context:warmingfirethermal erosion

Terrestrial Consumers

Caribou Voles and Lemmings

Wolf Spiders Songbirds 

Terrestrial Consumers

Caribou Voles and Lemmings

Wolf Spiders Songbirds 

Testing the Exploitation Ecosystem Hypothesis (EEH) Above‐ and Belowground

Oksanen and Oksanen 2000

0

100

200

300

400

500

600

700

0 100 200 300 400 500 600

Abo

vegr

ound

Pla

nt B

iom

ass

(g/m

2 )

Productivity (g/m2/yr)

A)

CT

+NP

-H

+NP-H

Open: MATClosed: DH

Gough et al. 2012 Ecology

Testing the Exploitation Ecosystem Hypothesis (EEH) Aboveground

Incorporating Trophic Interactions

Leaves and Stems

Roots andRhizomes

Live Vegetation

Leaves and Stems

Roots andRhizomes

Litter

InvertebrateHerbivores

BacteriaFungi

Soil Invertebrates

VertebrateHerbivores

Predators

Soil Nutrients

Root Exudates

Changing context:warmingfirethermal erosion

The Next Three Years

• monitoring, simulating, and modeling responses to climate change

• investigating disturbance effects– changes in consumers– fire– thermal erosion

• role of individual species and community structure in ecosystem processes

Mapping ArcLTER Objectives to Terrestrial Research

Terrestrial Research (This talk)

• “Shrubbification”– Landscape‐level response to warming– Long‐term fertilization experiments– Long‐term warming experiments– Identifying the pathways of change

• Disturbance– Vegetation resilience to fire– Successional response to thermal erosion

• Consumers– Mammalian herbivores alter response to increased nutrients

– Arthropod  consumers in shrub and open tundra

ArcLTER Shared Objectives

1. How does climate control ecosystem states, processes, and linkages?

2. How do disturbances change ecosystem states, processes, and linkages?

3. How do climate and disturbance interact to control biogeochemical cycles and biodiversity at catchment and landscape scales?

Questions?